This invention relates to video tape apparatus of the type in which a stationary control head detects control signals recorded in a longitudinal track on the tape. This invention is more particularly directed to an arrangement permitting so-called "single tape editing" in which the duty ratio of the control signals recorded on the control track is used for automatically controlling the tape transport speed of the video tape apparatus.
Whenever one or more video programs are recorded on a magnetic tape, various segments of the recorded program may be repetitive or otherwise unnecessary to the content of the overall video program on the tape. When the recorded video program is presented, it may be desirable to view certain of the recorded segments, and skip over the others, so that viewing time for the program is concentrated on the more interesting segments of the program.
In the so-called single-tape editing technique, an index or list is made of the recording time for the beginning and end of segments to be skipped over. Then, when the tape is played, an operator can fast-forward over the segments to be skipped, and play the remaining segments at normal speed.
One example of a possible application for the single-tape editing technique is in video-taped depositions of witnesses in preparation for a civil trial or other litigation. Many courts permit a previously video-taped deposition to be played back at the trial if, for example, a witness dies or becomes unavailable before trial. In such case, video-taped testimony that is not relevant, or testimony that is objected to, can be skipped over, with the remaining portions of the video taped testimony being played. In that case, it is desirable to use a single-tape-editing technique to reduce the amount of equipment required in editing the tape for presentation, and to reduce the cost of producing the edited tape.
Other examples of applications of such single-tape editing are in taped home video programs, and in broadcasts taped off the air, such as a sports event where it may be desirable to edit out the time out periods or other periods when there is no activity during the sports event.
However, conventional single-tape-editing techniques require that an index or list be made of precise times when the segments to be skipped over are reached. It is also necessary for a playback operator to manually set the video apparatus into a fast-forward mode when each segment to be skipped over is reached, and to set the apparatus back to a playback mode when the next segment of interest begins. Consequently, a considerable amount of error can occur in the playing of the tape. However, there has been no reliable single-tape-editing technique previously proposed for automatically playing back a prepared tape.